Powerline Networking - A Cabled Network Without Ethernet Cables

When it comes to networking your home or small office, I like to say "Ethernet for security and stability, WiFi for convenience". Unfortunately, you'll occasionally have a problem where you can't run Ethernet cables, and WiFi won't do the job either. Fortunately, any building with computers, and most without, has a third possibility - one that uses cables already installed - the power cables in the walls.

Ethernet Over Power, or Powerline Networking, is pretty simple. At each location where you need a network connection, you plug an EOP bridge into the wall, and an Ethernet cable connects to that. The other end of the Ethernet cable you connect to a single computer, or to a hub, switch, or router.

There are several vendor choices for EOP bridges, and here are 3 examples.

• Linksys PLEBR10
• Netgear HDX101
• Netgear XE102

Ethernet Over Power has its disadvantages, of which you must remain aware.

1. They have a limited market, so you'll have less choices and you'll find them relatively pricey, as compared to WiFi.
2. They are proprietary - each of the 3 choices above will only work with others in the same product line.
3. They use the 120V power circuits, and on a typical 240V service you will have to ensure that all units are plugged in to the same 120V half of the 240V.
4. Like WiFi, they are half duplex. All EOP devices, even if they will not network together, will still have to share the powerline signal spectrum.

Issue 1 is simple economics. More WiFi components are sold than Powerline Networking / Ethernet Over Powerline. More sales volume = more competition = lower prices = more sales volume. Look at the choices for WiFi, and compare that to EOP.

Issue 2 is unfortunate. The HDX101 and the XE102, even with both made by Netgear, will not participate in a network.

An HDX101 may coexist with HomePlug 1.0 products, but is not compatible nor interoperable with NETGEAR’s XE104, XEPS103, XE103, XE102 or WGXB102 Powerline products.

Issue 3 is a fascinating concern. In a typical domestic wiring system in the USA, you'll have a 240V service, which includes 2 hot leads providing the 240V. There will be a third lead, neutral, such that the neutral and either one of the hot leads, in combination, provides 120V. This is a 240V split service, providing 2 "legs" of 120V each.

Small appliances and light bulbs, in the USA, use 120V. With a 240V split service, half of the appliance / lighting circuits will be on one hot lead (1 "leg" of the service), and the other half on the other leg, providing a balanced load. When you setup your EOP bridges, they will all have to be on the same 120V leg, or there will be no signal between the bridges.

Essentially, you could (unreliably) have two EOP broadcast domains. All EOP devices on one leg will irregularly receive signals from the EOP devices on the other leg. When you turn on your kitchen stove, or other 240V appliance, you may get signals from one leg to the other; at other times, both legs will be isolated. If you don't plan for this to happen, you will learn it the hard way.

To identify which legs your prospective EOP bridge locations are on, examine your circuit breaker box. First, identify the breaker servicing each location. Verify the proper breaker, by plugging a lamp into the outlet, flipping the breaker, and watching the lamp go off then on. Having verified the breakers, examine their relative locations. Most breaker boxes will have the breakers arranged in two vertical columns, with alternating rows of breaker slots on different legs.

If you have two breakers vertically adjacent (in either column), it's likely that the two circuits will be on different legs. With breakers separated by 1 breaker slot, they will be on the same leg. With breakers separated by 2 breaker slots, they will be on different legs. And so on.

Note that two breakers, separated by a double width breaker (240V circuit, occupying 2 slots), will still be on opposite legs. Two slots (one double width breaker) is the same as two slots (two single width breakers); and the two breakers on opposite sides of the two slots will be on different legs.

Issue 4 is similar to WiFi. All EOP devices on the same service will have to asynchronously share the powerline signal spectrum, regardless of product line, and only one device can transmit at any time. The more EOP devices you have, the less efficient your powerline network will be. Despite different product lines being incompatible with each other, they all still have to share the powerline spectrum, as peers.

Despite the above problems, though, Powerline networking is a good solution when you can't run Ethernet cables, and when you can't get a WiFi signal to reach.

Note that EOP, for computer networking, is a relatively new technology. X-10 Remote Control Appliances / Lighting, which also sends signals over the AC power grid, is not. The problem of signal propagation on a 240V split service has been a long time problem for X-10 owners. There may be X-10 solutions that are usable in EOP scenarios. It's also likely that EOP and X-10 may be incompatible, on the same service or in the same neighbourhood. X-10 also makes remote (wireless) stereo speaker systems, which may present the same challenge.

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Ad-Hoc Networking

Microsoft Windows is called a Network Operating System. Computers running an operating system like Microsoft Windows (any of the many versions) were designed to be networked. As I've said elsewhere, if you have one computer, you have the beginning of a network.

The minimum complement of equipment, that you need for a computer network, is 2 computers and the appropriate networking components. The simplest networking component set would be two Ethernet adapters (one in each computer), connected by a bit of Ethernet cable, generally (but not always) a cross-over cable.

That's an ad-hoc Ethernet network. It's similar to hub (router / switch) based Ethernet networking, but without a hub (router / switch).

You can also have a network without any Ethernet cable, if you replace the Ethernet adapters with WiFi adapters. That's called an ad-hoc WiFi network.

An Ethernet based ad-hoc network is frequently limited to 2 computers. An Ethernet cable has just 2 ends - to get any more, you need a hub (router / switch). With a WiFi based ad-hoc network, you can have any number of computers connected, with minimal effort.

But there are several disadvantages to ad-hoc WiFi networking.

• One of the biggest is security. The minimum acceptable standard for WiFi security is WPA. Unfortunately, WPA requires a WiFi Access Point, to manage authentication / encryption. With no WAP, you're limited to using WEP to protect yourself, and WEP just isn't adequate security.
• With a router "in charge" of the network, you'll generally get more throughput. Client - server (with the server in charge) is more efficient than peer - peer (with no one in charge).
• Most WiFi equipment, in ad-hoc mode, will only operate in 802.11b mode, and get up to 11M of bandwidth total.
• Without a router, and a DHCP server built-in, you'll have to use ICS (if you're sharing Internet service), or pre-assign fixed IP addresses to each computer.
• You'll have to pre-assign channel number and SSID on each computer, as the normal WiFi Client won't find your ad-hoc network by scanning. Nor will it give you a signal strength indicator.
• You won't be able to disable SSID broadcast (not that this is a bad thing). In ad-hoc mode, SSID broadcast is forceably enabled.

Remaining aware of the limitations of ad-hoc WiFi, see specific details of the setup process

• About.Com How To Set Up an Ad Hoc (Peer) WiFi Network
• Microsoft Experts: Making the Wireless Home Network Connection in Windows XP Without a Router
• Microsoft Windows Vista Help: Set up a computer-to-computer (ad hoc) network
• Microsoft Windows XP Help: Set up a wireless network without a router

For a quick LAN, ad-hoc WiFi is OK. In an otherwise secure environment (maybe a single conference room deep within your office complex) it's perfect for a quick conference, and application sharing. For long term, really secure networking, though, you can't beat a properly setup, router (WAP) based network.

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Electrical Issues In Ethernet Networking

If you wire your house with Ethernet, you'll have a houseful of computers, all connected to the power system, and all connected to each other through the Ethernet network, and through the electrical system ("mains"). This is an obvious, but not trivial, issue.

With all computers connected within the same building, it's not a major issue. All computers are connected to the same main power supply, fed through the same power feed from the electric company, and grounded at the power distribution panel (electric meter et al). All computers, on properly maintained electrical and Ethernet networks, should have the same ground potential.

If you're lucky enough to have a large property, maybe you have a garage or shed out back of your house, with a separate electrical feed. If you decide to install a computer out there, networking that computer won't be a trivial issue. Getting past the issue of running cable between the two buildings (bury it, and risk underground problems), or string it through the air (and risk birds and other wildlife damage), you have a major code and safety issue.

Two separate buildings will have different ground potentials, amplifying the damage from lightning strikes. To fulfill electrical code requirements, you must ground electrical feeds, to separate buildings, separately. If you run Ethernet cable between your buildings, and lightning were to strike one building, the lightning would possibly travel from one computer to the other, through the Ethernet cable, and eventually to ground at the other building.

If you were unlucky enough to be working at either computer when this happened, you'd probably not live to worry about it. If you were lucky enough to not be in front of a computer, you could at least kiss the computers goodbye.

Even ignoring the possible damage from a lightning strike, a computer network with different computers connected at different ground potential won't do much for network stability. A properly functioning network depends upon ground at every network point having the same (identical) voltage level. Any variances, as can happen between any two separately grounded objects, will cause chronic and intermittent packet loss.

The bottom line? If you can't ground both ends of the Ethernet cable very securely, fiber or WiFi is a much better choice for connecting two separate buildings. Fiber-Optic cable doesn't conduct electricity, just light. And WiFi isn't a physical media at all.

If you have 2 buildings, limit the dangers of lightning to each building alone. Don't tie the two together, inadvertently.

For more discussion:

• Cabling Installation & Maintenance: Ground potentials and damage to LAN equipment
• Citel: Overview of Transient Overvoltages
• SelfHelp Forums: Cat 5 between buildings

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WiFi Authentication

When you setup your computers on your network, and your network is used by more than one person, you'll likely have files and folders on your computer that you don't want other people to access. Windows file sharing, and access permissions, is a complex subject with many issues to challenge you.

When you setup your WiFi LAN, you probably have simpler goals.

• Allow you (and your family, friends, co-workers, other folks you know) to connect to your LAN.
• Prevent folks you don't know from connecting to your LAN.

With these simple goals, you setup very simple security. Give everybody (every computer) a simple, pre-shared key. WPA-PSK is the simplest effective solution for securing your WiFi LAN.

Given the possibility that you might not want everybody to have WiFi access permanently, WPA-PSK may not be versatile enough for you. You can setup individual access, using 802.1x authentication, which generally uses a RADIUS server. To use 802.1x authentication, you have to setup 3 components.

• A RADIUS server.
• Your router or WiFi access point.
• Your WiFi clients.

If you select 802.1x authentication in the WiFi client setup, and you don't have a RADIUS server, your WiFi client will spend a lot of time needlessly trying to contact a RADIUS server. If your WiFi connection drops regularly and resumes with no action taken by you, or regularly hangs with high bandwidth peaks (say every 60 or 120 seconds), check your WiFi client, and make sure that 802.1x authentication is not enabled.

Interestingly enough, 802.1x authentication is a selectable feature on most client connections, Ethernet as well as WiFi. Selecting 802.1x authentication on an Ethernet LAN, without a RADIUS server, isn't usually a problem, as it is with WiFi.

You may also see odd behaviour like this, if you are running two or more WiFi clients.

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Automatic Metrics and The Ability To Roam Wirelessly

If you have a portable computer, and you've setup a WiFi LAN in your house or office, you'll enjoy the freedom of moving around the house, at will, while still connected to the LAN. Even so, sometimes there will be times when the WiFi connection isn't enough. You'll never get rid of Ethernet, completely.

Most portable computers come with an Ethernet adapter, and a WiFi adapter, installed and activated. The Automatic Metric feature in Windows XP let you leave both connections activated, and will use the fastest connection, that is working, at any time.

You can use automatic metrics (by default), or you can manually change the settings to prefer either connection, using the TCP/IP Properties - Advanced wizard.

NOTE: Using the Automatic Metric feature on a laptop having a role as a server on your LAN may cause problems with the browser infrastructure. Don't carry a server around without understanding the complications.

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Connecting Two Computers With A Crossover Cable

Most of my articles in this website are about Windows Networking / File Sharing, or about Internet Connectivity, and start by assuming that you have several computers, and a hub (router / switch) connecting them. But what if you have just 2 computers, and just want to quickly move files between the two? Or maybe you want to setup Internet service, for the 2 computers, without using a router to share the service?

You don't always require a hub (router / switch) to connect just 2 computers.

• Make The Right Decision
• Use The Proper Equipment
• Setup The Network - No Internet
• Setup The Network - With Internet
• Verify The Network
• Troubleshoot The Network, If Necessary

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Make The Right Decision
Start by asking yourself - what do you want to do - both now, and in the future? If you just want to immediately connect just these two computers, and quickly move files between the two, without Internet service, then this is the right start.

If your future might include Internet service, or if you might end up with a third computer, then you would really be better off using a hub (router / switch).

If you want to connect the two computers, and share Internet service, you can do that using a crossover cable. But know the issues before you start.

• If the computer with Internet service has it thru a dedicated modem, either:
  • Internally installed.
  • Connected externally, but thru a serial cable.
  • Connected externally, but thru a USB cable.
then using a crossover cable is a valid solution.
• If the computer with Internet service has it thru an Ethernet connection, or thru WiFi, then this is not a valid solution. If the Ethernet or WiFi connection is on subnet 192.168.0/24, this will not work at all. In the latter case, you will have to connect both computers directly to the LAN with subnet 192.168.0/24. If the Ethernet or WiFi connection has a private LAN address (10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/24), you're behind a NAT router, and you should setup a bridge, rather than use ICS.

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Use The Proper Equipment
The simplest solution, for networking just 2 computers, is to get an Ethernet crossover cable, and connect the two directly. A single crossover cable is the equivalent to getting a hub (router / switch), and a pair of straight-thru patch cables.

Please use Ethernet, not Firewire or USB, for connecting your computers. Firewire / USB networking requires extra drivers, and extra work. Ethernet drivers are native in all modern operating systems.

Please use a Cross-over Ethernet cable. A Straight-Thru, aka Patch, cable may work for some newer systems, which can automatically sense the need for a cross-over. But a cross-over cable will work all of the time, when you need to connect two computers directly.

Patch cables may come in many colours and lengths; some computer stores will have dozens of choices to suit your cabling needs. Cross-Over cables, when you find them in the store, will be explicitly labeled "Crossover", and will come in one colour (probably orange), and one length (probably 3 or 5 foot).

Please buy a properly made cross-over cable. If you're a masochist, or extremely desperate, you may make your own from a pair of patch cables, properly spliced. But Ethernet cables, that support modern high speed networks, require precision in their construction. I'm a fan of do-it-yourself activity (as in the reason for this website), when it's properly planned. I don't recommend do-it-yourself Ethernet cabling, when you're setting up a network. Buy a cable, unless you're very experienced with networking and can easily recognise the possible problems.

If you replace the two Ethernet adapters, one on each computer, with two WiFi adapters, you may be able to eliminate the Ethernet cable and setup an ad-hoc WiFi network. A WiFi based ad-hoc network isn't terribly different from an Ethernet based ad-hoc network, once you get the WiFi connectivity working.

Use the Device Manager in Windows, and test the network adapter in each computer. Connect your cross-over cable to the two network adapters. Observe the lights on the network adapters, and / or the status indicated by the Local Area Connection icon in the tooltray - do both computers indicate successful electrical connection?

Now, will you be setting up your network to Share Internet Service? Or just to share files, with No Internet Service?


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Setup The Network - No Internet
If you just have two computers, and no Internet service to either, run the Network Setup Wizard on each computer. Select the last option

This computer belongs to a network that does not have an Internet connection.

Having connected the two computers physically, and checked that you have no physical problems, you need to make the logical (TCP/IP) settings. If you have Windows XP / Vista, or other current operating systems on your computers, you're in luck. Modern operating systems use a system called APIPA, and should be able to provide ip settings automatically, so the two computers will connect to each other. If you allow the two computers to dynamically assign addresses, APIPA should take care of this for you.

Be prepared to get an error message - Limited Or No Connectivity - if you use APIPA configuration.

NOTE: if any of your computers are NOT running Windows XP / Vista, you'll have to set the IP address and subnet mask manually, on those computers. Remember IP addresses have to be unique for IP addressing to work.

• Run "ipconfig /all", from a command window, on each APIPA compliant computer first.
• Make a list of which addresses are automatically assigned.
• Manually configure each non-APIPA compliant computer.
  • Set each computer up with a unique IP address, in the 169.254.x.x subnet (written as 169.254/16 in many cases).
  • Each computer gets a subnet mask of "255.255.0.0".
  • Each computer gets an IP address of "169.254.x.x", where the "x.x" MUST be different for each computer. Check your list of addresses assigned by APIPA!
    
  • Each value of "x" must fall between 1 and 255 (not including either 1 or 255).
  • You assign IP addresses using the TCP/IP Properties wizard. Select "Use the following IP address". Only worry about IP address and Subnet mask - the other settings are only useful if you have an outside connection. With locally connected computers, just IP address and Subnet mask are essential, and should be assigned as described above.

Having connected the two computers physically, and checked that you have no physical problems, next Verify The Network - make sure that it works properly.


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Setup The Network - With Internet
If you have two or more computers, with Internet service to one, and wish to share the service to the others, run the Network Setup Wizard, first, on the computer that has Internet service. Select the first option

This computer connects directly to the Internet. The other computers on my network connect to the Internet through this computer.

You'll probably be running ICS on this computer. Note the disadvantages and requirements of ICS, and a possible alternative. You'll have to have two separate network connections (one might be a modem, directly or internally connected). You'll indicate which connection provides the Internet service, and then which connection(s) are to be used for sharing the Internet service.

If, per the ICS alternative, you decide to use a bridge, remember that both of the network adapters, on the bridged computer, will have the same IP address. Plan your testing accordingly.

If you decide to use ICS, run the Network Setup Wizard on the other computers, and select the second option

This computer connects to the Internet through another computer on my network or through a residential gateway.

If you can't run the Network Setup Wizard on any computers, use the TCP/IP Properties wizard, and select automatic configuration.

If the second computer will be running as a server, and providing data to the Internet, remember that the ICS server will have to be online constantly. Having dealt with that requirement, setup the ICS server to (KB231162): forward the right ports to the Internet server.

Having connected the two computers physically, and checked that you have no physical problems, verify that the network works properly.


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Verify The Network
Please verify that you have connectivity between the computers first.

• Run "ipconfig /all" on each computer, from a command window. Note the IP address and subnet mask for each network connection.
• Make sure that you don't have a bridge, on any computer, unintentionally.
• Verify that all computers are on the same subnet, and that each has a unique address.
  • If this is two computers without Internet service, each computer should have an address of 169.254.n.n, and a subnet mask of 255.255.0.0. This will indicate that each is on subnet 169.254/16.
  • If this is two, or more, computers sharing Internet service, the first computer (thru which the others will be getting Internet service) must have an address of 192.168.0.1, and a subnet mask of 255.255.255.0 (on the connection used for sharing the Internet service). All of the computers getting Internet service thru the first computer must have an address of 192.168.n.n, and a subnet mask of 255.255.255.0, and show both DHCP and Autoconfiguration Enabled = Yes.
• From each computer, again in a command window, ping the other. If, for instance, the address on Computer B is "169.254.1.2", open a command window on Computer A, and enter:
  

  ping 169.254.1.2

  
  If you get back a series of responses like
  

  Reply from 169.254.1.2: bytes=32 time<1ms TTL=128
  Reply from 169.254.1.2: bytes=32 time<1ms TTL=128
  Reply from 169.254.1.2: bytes=32 time<1ms TTL=128
  Reply from 169.254.1.2: bytes=32 time<1ms TTL=128

  
  then you are ready.

When you open Windows Explorer on each computer, and look in Network Neighborhood, you should see both computers. And when you open (doubleclick on) one entry, you should see the folders and files.

And, if the computer directly connected to Internet service can access the Internet, the other computers should be able to do so also.


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Troubleshoot The Network, If Necessary
So what if it doesn't work, per the basic testing above? Well, now you start troubleshooting, and methodically, in the right sequence.

• Verify physical connectivity again.
• Troubleshoot Windows Networking.
• Troubleshoot File Sharing.
• And, having done ALL of the above, post in a forum where the experts give serious help, and Ask For Help, with details provided.

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